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- Author or Editor: R. Frouin x
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Abstract
Day–night surface temperature differences measured in the infrared (10.5–12.5 μm channel) by the HCMR satellite experiment frequently show large diurnal heating (several °C) of the upper layer of the ocean during the summer months in the Mediterranean Sea when the wind speed is low. When observed in the 0.5–1.1 μm channel, glitter reflectance—i.e., direct solar radiation specularly reflected towards the sensor—correlates with diurnal heating. Glitter reflectance has been modeled to retrieve an equivalent wind speed. Observed diurnal heating (ΔT) do not exceed 5°C, in agreement with the limit value calculated from the heat transfer equation assuming thermal diffusivity is only molecular. The influence of wind speed can be approximately described by ΔT=0.4U −1+0.5 (in °C for U in m s−1), for U less than 2 m s−1. A mean diurnal heating of nearly 1°C is calculated for the marine coastal areas of southern France. During this period, satellite observations should be restricted to night and early morning orbits, or to periods of high wind speed (U>5 m s−1).
Abstract
Day–night surface temperature differences measured in the infrared (10.5–12.5 μm channel) by the HCMR satellite experiment frequently show large diurnal heating (several °C) of the upper layer of the ocean during the summer months in the Mediterranean Sea when the wind speed is low. When observed in the 0.5–1.1 μm channel, glitter reflectance—i.e., direct solar radiation specularly reflected towards the sensor—correlates with diurnal heating. Glitter reflectance has been modeled to retrieve an equivalent wind speed. Observed diurnal heating (ΔT) do not exceed 5°C, in agreement with the limit value calculated from the heat transfer equation assuming thermal diffusivity is only molecular. The influence of wind speed can be approximately described by ΔT=0.4U −1+0.5 (in °C for U in m s−1), for U less than 2 m s−1. A mean diurnal heating of nearly 1°C is calculated for the marine coastal areas of southern France. During this period, satellite observations should be restricted to night and early morning orbits, or to periods of high wind speed (U>5 m s−1).
Abstract
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Abstract
Satellite infrared data have been used to investigate the mesoscale variability of the SST (sea surface temperature) field. A statistical analysis of the SST field has been performed by means of the structure function. Results give the equivalent power-law exponent n of the spatial variance density spectrum E(k) ∼ k −h . The exponent n was found to vary from 1.5 to 2,3 with a mean value of 1.8 in the ]range of scales 3–100 km which is in agreement with previous one-dimensional analysis from shipborne and airborne measurements. These observed values of n are discussed and compared with the values predicted by turbulence theories.
Abstract
Satellite infrared data have been used to investigate the mesoscale variability of the SST (sea surface temperature) field. A statistical analysis of the SST field has been performed by means of the structure function. Results give the equivalent power-law exponent n of the spatial variance density spectrum E(k) ∼ k −h . The exponent n was found to vary from 1.5 to 2,3 with a mean value of 1.8 in the ]range of scales 3–100 km which is in agreement with previous one-dimensional analysis from shipborne and airborne measurements. These observed values of n are discussed and compared with the values predicted by turbulence theories.
